<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>flex-example</title>
</head>
<!--
  主轴方向
  flex-direction: [row|row-reverse|column|column-reverse]
  纵轴线
  flex-wrap:[nowarp|wrap|wrap-reverse]
  flex-flow:<flex-direction> || <flex-wrap>
  主轴对齐方式
  jusfify-content
  align-items
  align-content

  main axis: 水平主轴
  cross axis: 交叉轴
-->
<body>

</body>
</html>